This invention is in the field of curable epoxy and polyester resin compositions. More particularly, it is in the field of curable thixotropic epoxy and polyester resin compositions which are useful for building or repairing fiber glass-polyester or epoxy boats and for repairing fiber glass-polyester or epoxy vehicle bodies.
A thixotropic polyester resin composition can be prepared by admixing ultrafine polypropylene fibers having a length of about 1-100 microns and a diameter of about 0.05-2 microns with a polyester resin composition comprising a polyester resin of a polyhydroxy alcohol (including a dihydroxy alcohol) and an unsaturated polycarboxylic acid (including an unsaturated dicarboxylic acid).
Ultrafine polymeric fibers (which are also known as ultrafine plastic fibers) are well known to those skilled in the art and methods for preparing such fibers are also well known.
U.S. Pat. No. 3,099,067 (139/420 Merriam et al) teaches that such fibers can be prepared by;
A. EXTRUDING A MIXTURE OF TWO OR MORE NORMALLY SOLID MUTUALLY INCOMPATIBLE THERMOPLASTIC RESINS TO FORM A COMPOSITE MONOFILAMENT HAVING AS ITS MINOR COMPONENT THE RESIN MATERIAL FROM WHICH THE ULTRAFINE FIBER IS TO BE FORMED;
B. DISSOLVING THE MAJOR RESIN COMPONENT OF THE MONOFILAMENT IN A SOLVENT IN WHICH THE MINOR COMPONENT IS INSOLUBLE OR SUBSTANTIALLY INSOLUBLE; AND
C. RECOVERING THE RESULTING ULTRAFINE FIBER.
U.S. Pat. No. 3,549,734 (264/37 Yasuda et al.) teaches the preparation of ultrafine polypropylene fibers by such technique wherein polystyrene is extruded with polypropylene using the polypropylene as the minor component of the resulting composite fiber. The polystyrene is dissolved in benzene leaving an ultrafine polypropylene fiber which is recovered.
An article by Miller et al (Textile Research Journal, December 1973, pp 728-733) teaches a similar method for preparing ultrafine polypropylene fibers having diameters in the range of 0.05-1 micron. Miller et al use an admixture of polypropylene and an ethylene-acrylic acid copolymer salt to form their ultrafine polypropylene fibers.
The above-mentioned Merriam et al reference also teaches that ultrafine polymeric fibers can be prepared by subjecting a molten polymer to the action of a high velocity jet of gas. A method for using this technique comprises spreading a molten polymer heated to a highly fluid condition on a heated surface to form a film of molten polymer on the surface and subjecting such film to a blast of hot gas or vapor. This causes small globules of the molten polymer to form. The jet of hot gas breaks the small globules into ultrafine fibers. As these fibers are moved by the gas stream cooling occurs and the fibers become rigid and are broken into segments by the stream of gas in which they are suspended. The segments are collected on a screen or other surface in the form of an entangled mat which is recovered.
Another method useful for preparing ultrafine fibers of a thermoplastic polymer comprises extruding the thermoplastic polymer through a die which has its die openings arranged in a circle. The extruded polymer is contacted with a stream of hot gas which attenuates the extruded polymer into ultrafine fibers. U.S. Pat. No. 3,615,995 (156/161, Butin et al) and U.S. Pat. No. 3,595,245 (131/269, Butin et al) teach the use of such technique to produce ultrafine polypropylene fibers. U.S. Pat. No. 3,773,590 (156/244, Morgan) teaches the production of a mat of ultrafine polypropylene fibers.
U.S. Pat. No. 3,293,205 (260/37, Doyle et al) teaches the use of finely divided polyoxymethylene fibers to thicken liquid polyester compositions and U.S. Pat. No. 3,354,114 (260/40, Doyle) teaches the use of finely divided polystyrene fibers to thicken polyester compositions. These patents teach the use of a fluid energy mill to prepare short fibers from long polyoxymethylene and long polystyrene fibers.